Xsere Raid remove a misbehaving HDD from the array

> There's a spare on the other side, but for some reason it's not used. (I understood that it would be used by either controllers if needed)

The two 'sides' of an Xserve RAID are, essentially, independent - you have more like 2 x 7-disk enclosures rather than 1 x 14.

Therefore if a drive fails on the either side, it can only use a spare disk on the same side for automatic rebuilds.

> I'd like to just remove the faulty disk from the Array. So to make the array smaller. Is this possible?

No. There is no support in Xserve RAID for reducing the size of an array, other than via destroying the array and building a new one.

What you can do is remove the failed drive and replace it with the spare drive from the other side. This will make the spare available to the left-side controller and it can rebuild the array on that drive to restore performance/redundancy.

Of course, this now leaves you vulnerable to a subsequent disk failure. Maybe you've been lucky so far... but it may also be the case that the drives are starting to wear and the other drives may fail soon.

Given the high cost of replacement drives for the Xserve RAID, the fact that most supplies at this point are likely used/refurbished and at the same point in their lifecycle, coupled with the precipitous drop in drive prices over the last 10(?) years or so, you might want to look at other options - you can probably pick up a decent 4TB array for less than the cost of a single Xserve RAID disk.

> Should I do the swap while the unit is turned off or while in use?

It's fine to do it while powered.

Remove the failed drive.

Remove the spare drive from the RHS and install it in the spare slot on the left

You'll need to use RAID Admin to reset this drive to make it available. Then just let the array do it's rebuild.

> When you say 4TB array do you mean like a desktop hdd enclosure with one disk or something like Drobo? I was thinking also about using the Xserve drivebays, but they need specific models and SATA I...

Yes, I mean like a desktop enclosure. Drobo would be a good bet, but there are others to consider, too.

You can't use the Xserve RAID enclosure since it requires SATA drives and only support up to 400GB (or 500GB with the latest(!) models). Larger drives just won't work.

Your ears may also thank you, too. :)